----Facts---- 1) The marking is on all boards, irrespective of date code 2) It only happens on leads that have been selective soldered 3) The pattern of white spots is consistent with flux spraying (the spots are around the solder joints fanning out) 4) The solder mask is a black colored LPI mask in 1 assy & transparent green on the other 5) The problem doesn't happen when using wave solder & same selective solder flux 6) The boards have already gone through an SMT placement-oven-wash twice (top & bottom) by the time they reach selective solder 7) Selective solder performance is fantastic with other PCBAs 8) Both assys are lead-free/RoHS compliant products